Prosensa Corporate Overview Jefferies Healthcare Conference London, - PowerPoint PPT Presentation

Prosensa Corporate Overview Jefferies Healthcare Conference London, UK November 19, 2014 Hans Schikan, CEO

Forward-Looking Statements This presentation may contain statements that constitute “forward -looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Forward-looking statements are statements other than historical fact and may include statements that address future operating, financial or business performance or Prosensa’s strategies or expectations. In some cases, you can identify these statements by forward-looking words such as “may,” “might,” “will,” “should,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,” “projects,” “potential,” “outlook” or “continue,” and other comparable terminology. Forward-looking statements are based on management’s current expectations and beliefs and involve significant risks and uncertainties that could cause actual results, developments and business decisions to differ materially from those contemplated by these statements. These risks and uncertainties include, but are not limited to, the timing and conduct of clinical trials of drisapersen and Prosensa’s other product candidates, plans to pursue research and development of product candidates for DMD and other indications, the clinical utility of Prosensa’s product candidates, the timing or likelihood of regulatory filings and approvals, Prosensa’s intellectual property position, expectations regarding payments under Prosensa’s collaborations and Prosensa’s competitive position. These risks and uncertainties also include those described under the captions “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Prosensa’s Annual Report on Form 20-F and other filings with the Securities and Exchange Commission. Forward-looking statements speak only as of the date they are made, and Prosensa does not undertake any obligation to update them in light of new information, future developments or otherwise, except as may be required under applicable law. All forward-looking statements are qualified in their entirety by this cautionary statement .

Our Mission To develop innovative, RNA-modulating therapeutics to fill unmet medical needs for patients with rare genetic diseases 2

Corporate Highlights Rare disease company based in the Netherlands, listed on Nasdaq (RNA) Largest pipeline and clinical program in Duchenne muscular dystrophy (DMD) NDA submission under accelerated approval for drisapersen underway, followed by MAA in EU for conditional approval Orphan Drug status for 6 DMD compounds FDA Breakthrough Therapy Designation for drisapersen Solid intellectual property position Management with extensive experience in commercializing orphan drugs Cash position (Sept 30, 2014): EUR 62M ; Cash burn (FY-2013): EUR 22M ; (H1-2014): EUR 12.7M; YE 2014 cash balance guidance: EUR 52-54M 3

Our Science - RNA Modulation Technology platform enables us to design sequences of nucleotides that bind to specified regions of pre-mRNA which may induce exon skipping or exon inclusion, reduce mutated toxic RNA or protein, remove specific protein domains or block protein expression 4

R&D - Largest Pipeline in DMD Indication Compound Discovery Pre-Clinical Phase I/II Phase III Drisapersen 13% of DMD patients 6% of DMD patients PRO044 PRO045 8% of DMD patients Duchenne 8% of DMD patients Muscular PRO053 Dystrophy 4% of DMD patients PRO052 PRO055 2% of DMD patients PROSPECT Huntington’s PRO289 Disease Myotonic PRO135 Dystrophy 5

Duchenne Muscular Dystrophy (DMD) Severely debilitating and invariably fatal progressive neuromuscular disease X-linked, rare genetic disease Evolution of clinical symptoms of DMD Rapid progression of muscle degeneration 0 5 10 15 20 25 30 Age 75,000 patients in addressable populations walking problems wheelchair - skeletal deformity very limited use of arms ventilation at night ventilation 24h death 6

DMD Natural History and Endpoints 6MWT is a validated functional endpoint for DMD and other rare diseases Age & baseline walking ability are important variables that determine decline in the ability to walk as measured by 6MWT* Recent publication suggests clinically meaningful change in walking ability, as measured by 6MWT, to be in the range of 20-30 meters * Creatine Kinase (CK) is a marker of muscle damage - DMD patients have elevated levels of CK in their blood serum Prosensa has completed enrollment with 269 patients in an observational study to characterize the natural history and progression of DMD in addition to capturing potential biomarkers 7 * McDonald, Muscle & Nerve 2013

Functional Outcome - 6MWT Conceptual Representation Based on natural history, DMD boys lose approximately 40-60 meters in 6MWT per year 6-Minute Walk Distance, m 700 Early intervention 600 500 400 300 200 Late intervention 100 5 7 10 Approx. age years 8

Lead Compound - Drisapersen  20-mer Antisense Oligonucleotide (AON) with specific binding to exon 51 of dystrophin gene pre-mRNA  Administered by once weekly subcutaneous injection (6mg/kg)  May address up to 13% of all DMD patients  Granted orphan drug status in US, EU, Japan, Australia  Breakthrough Therapy designation granted by the FDA  NDA submission initiated under rolling review and Fast Track status  Issued patents include US patent expiring 2023; EU patent expiring 2021 9

Drisapersen Clinical Program More than 300 patients and over 450 patient treatment years in global clinical program Study Phase Study design N Status Phase I/II + Open label, repeat dose escalation (extension phase Complete; CLIN-02 12 Extension 6 mg/kg/wk intermittent); extension ongoing DMD114673 Placebo-controlled, pharmacokinetics/safety; single DEMAND I Phase I 20 Complete DMD114118 dose Exploratory placebo-controlled, DEMAND II Phase II 53 Complete dose regimen comparison; ex-US, 24/48 wks DMD114117 Randomized, placebo-controlled, DEMAND III Phase III 186 Complete confirmatory study; global, 48 wks DMD114044 Phase II/III Open label, extension study for DEMAND II) & DEMAND IV 234 Closed Extension DEMAND III ; 96 wks DMD114349 Exploratory placebo-controlled, DEMAND V Phase II 51 Complete dose-comparison; US only, 24 wks DMD114876 Phase II/III Open-label, extension study for US & Canadian DMD115501 72 Recruiting Extension subjects from DEMAND III, IV, V 10

Overview of Supportive Studies + Analyses Clinically meaningful treatment difference across program; DEMAND III outlier 11 *pb = placebo (DEMAND IV: pb/delayed treatment); dr = drisapersen 6 mg/kg; Tx difference on 6MWD; not all analyses shown

Long Term Study DMD114673 Efficacy results up to 3.4 years (177 weeks) appear to show delay of disease progression 800 Age at N=10 week 177 700 13.7 Distance walked (m) 14.3 600 11.4 500 12.6 400 10.9 9.3 300 13.3 200 15.4 8 weeks on – 4 weeks off 100 13.0 14.8 0 0 12 24 36 48 60 72 80 93 105 117 129 141 153 165 177 Weeks Mean age is 12.9 years at 177 wks 12

Long Term Study DMD114673 Long-term data suggest stabilization on 6MWT Ambulant boys: Mean change from baseline: +33 m N=8 Distance walked (m) [Median change from baseline: +64 m] All boys: N=10 Mean change from baseline: -25 m [Median change from baseline: +8 m] Weeks 13

Functional Outcome - 6 Minute Walk Test DMD patients lose approximately 40-60 m in 6MWD in 1 year, 150 m in 3 years Δ 6 MWT SD Study Study Design N (m) (m) (years) McDonald 2010¹ Natural History -57 104 1 18 Ataluren 2010¹ Placebo arm -42 90 1 57 Mazzone 2011² Natural History -42 74 1 71 Goemans 2012¹ Natural History -38 96 1 19 McDonald 2013² Natural History -59 82 1 33 Mazzone 2013² Natural History -122 78-97 2 113⁴ Goemans 2013² Natural History -125 139 2 14 Pane, 2014³ Natural History -146 146 3 68 ¹ All ages; ²Age >7, ³Age ≥7, ⁴ All patients in study 14

Placebo Controlled Studies - 6MWD Two placebo-controlled studies show treatment benefit on 6MWD Placebo Drisapersen 6 mg/kg/week Δ 6MWD = +35m p=0.014 Δ 6MWD = +31m Δ 6MWD = +27m p=0.003 p=0.069 +32m (n=18) +20m (n=36) 20 +16m (n=18) -4m (n=18) -11m (n=16) -11m (n=34) (11) DEMAND II DEMAND V DEMAND II + DEMAND V (DMD114117) (DMD114876) (DMD114117 + DMD114876) (25 week endpoint) (24 week endpoint) (post-hoc analysis 24/25 weeks) 15

DEMAND III by Age and Baseline 6MWD Unadjusted Treatment Adjusted Visit Treatment N n mean baseline difference 95% CI P-value mean (se) value (sd) (m) All Subjects Placebo 61 59 348 (92) -53 (10) Week 48 Drisapersen 125 117 337 (96) -42 (7) +10 (-15,35) 0.415 ≤ 7 years at baseline Placebo 29 29 383 (67) -25 (11) Week 48 Drisapersen 51 50 368 (65) -4 (9) +21 (-7,50) 0.131 > 7 years at baseline † Placebo 32 30 316 (101) -83 (16) Week 48 Drisapersen 74 67 316 (107) -76 (11) +7 (-29,43) 0.703 > 7 years at baseline, and baseline 6MWD ≥300m and ≤450 m Placebo 15 14 351 (34) -67 (20) Week 48 Drisapersen 34 33 375 (42) -42 (13) +25 (22,72) 0.292 Model includes terms for Treatment, Visit, Treatment by Visit, Study, Baseline 6MWD and Baseline 6MWD by Visit † Includes subjects >11 years of age: drisapersen, n=11; placebo, n=1